Kashrut of Vitamins year round

Hello,

I have several questions regarding supplemental  Vitamins year round kosher status.

1) Are they considered a food item or can i swallow for example and omega 3 pill that uses oil from crustacean shellfish?

2) if non kosher ingredients are not allowed, is a statement on the packaging saying that it is made with “Anchovies and/or herring and/or mackerel and/or sardines” along with a disclaimer saying”no crustacean shellfish” enough to consider it kosher?

3) if non kosher ingredients are allowed for pills that I just swallow and don’t enjoy, would it still be ok for chewable ones that have an enjoyable flavor?

4) I take multiple vitamins every day because if i stop taking them for a while it causes health issues serious enough to make life very difficult, in other words to me they are like medicine that i need to take every day.

Does that have any effect on the Halakhas concerning their Kashrut status?

5) Do you have resources available or recommendations what to study  to learn more in depth about the methodology behind the answers or sources.

Thank you